Vehicular Communications and the WAVE Standard
The IEEE 802.11p specifies wireless access to vehicular environments (WAVE). This standard supports intelligent transportation systems (ITS). The current standard specifies transceivers with a single antenna, and orthogonal frequency-division multiplexing (OFDM) for the modulation technique at the physical layer (PHY). WAVE transceivers include mobile transceiver in vehicles, and stationary road side units (RSUS). The WAVE network can also be used in other mobile environments, such as railways, and water ways.
Multi-Antennas
Generally, multiple antennas transceivers improve throughput and reliability. A number of wireless standards specify OFDM and multiple nput multiple output (MIMO) technologies. These include IEEE 802.16, IEEE 802.11n, and 3GPP LTE (long term evolution).
However, MIMO requires accurate channel state information (CSI), and complex digital processing at the receiver. Providing CSI to the transmitter can require large overhead due to time varying nature of the channel caused by the fast velocity of WAVE transceivers.
Beam forming improves the reliability of focusing an array pattern in a directed beam. That is, the antenna array has a spatially dependent gain that amplifies signals based on there angle of arrival, see Godara “Applications of Antenna Arrays to Mobile Communications, Part I: Performance Improvement, Feasibility, and System Considerations”, Proceedings of the IEEE, Vol. 85, No. 7, pp. 1031-1060, 1997.
The goal of the invention is to improve reliability in WAVE networks using multiple antennas.